Perchlorate

The National Research Council's report on perchlorate has been used to support stricter controls on perchlorate than we have now. It's also been cited to support looser controls. What does the report actually say?

What the report does propose is a safe daily dose of the chemical, regardless of the source. It says that up to 0.0007 milligrams per kilogram (mg/kg) of body weight can be consumed daily without adversely affecting even the most sensitive populations – fetuses of pregnant women with thyroid problems.

This reference dose is based on human clinical studies, observing the actual effect on actual humans of different perchlorate doses. Below 0.007 mg/kg (ten times the reference dose), no effect on iodine uptake was observed. Also,

...the Research Council committee concluded that it was highly unlikely that disruption of thyroid function from perchlorate exposure would lead to thyroid cancer in humans.

So, bottom line?

Six weeks after the report's release, EPA announced that it was officially adopting the committee's reference dose. The agency determined that the dose corresponds with a drinking-water equivalent concentration of 24.5 parts per billion, but that perchlorate concentrations in food and milk still need to be examined.

And remember, that includes a safety factor of ten. Without that margin, we're looking at an allowable daily dose of 245 parts per billion.